‘Dissolving’ Styrofoam in Acetone

When expanded polystyrene foam is placed in acetone (propanone), it appears to dissolve, dramatically shrinking in volume. This striking demonstration shows how acetone breaks down the foam structure by dissolving the polystyrene polymer, leaving only a small residue of solid polymer behind.

1. Place a small volume of acetone in a glass beaker or other suitable container.
2. Take pieces of expanded polystyrene foam (such as packaging material or cups).
3. Drop the polystyrene foam into the acetone and observe.
4. Notice that the foam rapidly collapses, seemingly disappearing.
5. Compare the large starting volume of polystyrene with the small residue left behind.

Styrofoam VS Acetone - Let's Melt This:

A huge bar of polystyrene vs. a few milliliters of acetone - MEL Science:

📄 ‘Dissolving’ polystyrene in acetone - Royal Society of Chemistry: https://edu.rsc.org/experiments/dissolving-polystyrene-in-acetone/1721.article

• Try using different sources of expanded polystyrene, such as cups, packaging peanuts, or insulation boards.
• Collect the remaining polymer and allow it to harden into a dense plastic solid.
• Test other solvents (such as ethyl acetate or toluene) to compare their effects on polystyrene.
• Measure how much polystyrene can be absorbed into a fixed volume of acetone.

• Wear safety goggles and gloves when handling acetone.
• Conduct the demonstration in a well-ventilated area or fume hood to avoid inhaling vapors.
• Keep acetone away from flames or sparks, as it is highly flammable.
• Dispose of the resulting plastic residue and solvent safely, following local chemical disposal guidelines.
• Do not allow students to touch acetone directly.

• Why does polystyrene foam collapse so dramatically in acetone?
• Why does the volume decrease so much, yet some solid polymer remains?
• How does this demonstration illustrate the difference between a material’s structure (foam vs. solid polymer) and its composition?
• What environmental concerns are related to polystyrene waste and solvents like acetone?